Studies on human triosephosphate isomerase. III. Characterization of the enzyme from patients with the cri du chat syndrome

Triosephosphate isomerase has been studied in five patients with the cri du chat syndrome. Each of the patients showed the typical phenotypic and clinical expression of the genetic aberration. This group of patients exhibited three different karyotypic forms: a deletion of the short arm of chromosome no. 5, a ring chromosome, and an apparently normal chromosome no. 5. Triosephosphate isomerase from all of the patients was normal with respect to total activity, catalytic constants, and heat stability. The normal distribution of the three triosephosphate isomerase isoenzymes was confirmed by starch gel electrophoresis and isoelectric focusing. Thus, it is concluded that the genes for triosephosphate isomerase are not localized on the short arm of chromosome no. 5, as had been previously suggested.